The present invention relates to shared media networks, such as cellular telephone networks, and, more particularly, to a method for tracking and paging users of such networks.
The growing demand for Personal Communication Services (PCS) increases the need for efficient utilization of the limited radio resources available for wireless communication. The present invention is concerned with the utilization of the wireless resources devoted to location management. The problem addressed by the present invention is the minimization of the wireless cost of mobile user tracking in PCS networks.
The utilization of wireless network resources for mobile user tracking has been addressed by many studies. Basically, there are two extreme strategies that may be used for user tracking. In the first strategy, known as "Never Update", the user never updates its location. Thus, whenever there is a need to set up an incoming call directed to the user, the system must search for him/her all over the network. In the other extreme strategy, known as "Always Update", the network continuously keeps track of the user location. Various strategies which combine these two extremes have been proposed in the literature. Examples of these strategies include C. Rose and R. Yates, "Minimizing the Average Cost of Paging Under Delay Constraints", ACM Journal of Wireless Networks, Vol. 1, No. 2, pp. 211-219, 1995; A. Bar-Noy and I. Kessler, "Tracking Mobile Users in Wireless Networks", IEEE Trans. on Information Theory, Vol. 39, pp. 1877-1886, November 1993; A. Bar-Noy, I. Kessler and M. Sidi, "Mobile Users: To Update Or Not to Update?". Wireless Networks, Vol. 1, No. 2, pp. 175-185, 1995; C. Rose, "Minimizing the Average Cost of Paging and Registration: A Timer-Based Method", ACM Journal of Wireless Networks, Vol. 2, No. 2, pp. 109-116, 1996; J. Ho and I. F. Akyildiz, "Mobile User Location Update and Paging Under Delay Constraints", Wireless Networks, Vol. 1, pp. 413-425, 1995; U. Madhow, L. Honig, and K. Steiglitz, "Optimization of Wireless Resources for Personal Communications Mobility Tracking" IEEE Trans. on Networking, Vol. 3, No. 6, pp. 698-707, 1995; and S. Tabbane, "An Alternative Strategy for Location Tracking", IEEE JSAC, Vol. 13, No. 5, pp. 880-892, 1995.
The basic idea shared by these papers is known as the "Partial registration" strategy. Namely, upon location change a user may or may not update its new location. The criterion for user registration may be static, such as network partition into location areas. For example, in the GSM system the network is partitioned into groups of cells, referred to as location areas. A user updates its location each time it changes a location area, while within a location area it uses the "Never Update" strategy. Because the partition into location areas is static, and done by the system, not accounting for the user dynamic behavior, this strategy is termed "static". Another type of partial registration strategy is the dynamic strategy, in which each user decides when and where to update its location. The criterion for user registration may be a function of time (Rose, 1996), distance from last known location (Bar-Noy et al. 1995; Madhow et al., 1995), number of movements between cells (Bar-Noy et al., 1995), or based on personal location profile (Tabbane, 1995). All the dynamic partial registration strategies mentioned above are implemented solely on user equipment. As such, they ignore the system activity, and depend solely on the user activity.
The optimal solution which minimizes the user tacking cost using these methods is of high computational complexity, and often requires a dynamic programming method. Some of these strategies (such as the distance based strategy) require information that is not generally available to the user. Thus, an implementation of an optimal solution on the user equipment is not feasible, due to commercial, maintenance and reliability reasons. In practice, users may register using a fixed, pre-defined parameter (timer, distance, etc.), regardless of the exact details of user activity. Clearly, the performance of such an implementation is inferior to the optimal strategy. In addition, because the user decision whether to register (update) or not to register ignores the status of other users in the network, as well as the total load on the network, the likelihood of collision is expected to be very high, especially at high load periods.
There is thus a widely recognized need for, and it would be highly advantageous to have, a method of mobile user tracking in PCS networks that would overcome the disadvantages of presently known methods as described above.